This invention consists of a system for the calculation of at least one vehicular traffic check parameter.
This invention is particularly applicable to all types of automobile vehicles (cars, trucks, etc.) travelling on all sorts of roads (motorways, interstate roads, state roads, etc.). However we will see that the system in the invention can also check river and sea traffic, or objects passing along a robotized line. Thus the term vehicle refers equally well to cars, trucks, motor cycles, boats, objects, etc.
In the specific field of automobile vehicles, an attempt is made to do a traffic analysis at a specific point in order to deduce a number of parameters. The parameters in which we are interested are particularly:
the number of vehicles travelling on each lane during a pre-defined time interval; PA1 the speed of these vehicles; PA1 the average and harmonic speed of a set of vehicles; PA1 the percentage of trucks; PA1 the occupancy ratio in each lane, . . . .
At the present time three main techniques are used for the analysis of road and motorway traffic:
The first very widely used technique is to place induction loops under the road. Field variations induced in these loops determine whether or not a vehicle has passed.
The main advantage of this technique is the fact that induction loops work under all climatic conditions, both during the day or night. However it is difficult and expensive to install these induction loops, and it is difficult or even impossible to perform any maintenance. Furthermore, it is difficult to do more than count vehicles.
The second technique still at the prototype stage consists of using video cameras and processing the captured pictures. It is very easy to install these cameras on masts, but performances are not very conclusive: video cameras do not have the advantage of working under all climatic conditions, and are also very dependent on luminosity conditions. Moreover the algorithms used in picture processing are complex and require high computing capacity.
Finally the third known technique consists of installing a fixed continuous wave radar, for example on a bridge infrastructure, and detecting vehicles and their speed using the Doppler effect.
This type of technique, in which associated processing can extract various parameters concerning vehicular traffic (speed, length) is described, for example, in U.S. Pat. No. 4,985,705.
Although the continuous wave radar satisfies compactness, ease of installation and day and night operation requirements and is independent of climatic conditions, it can only check a single traffic lane. Therefore one radar is necessary for each lane in a 6 to 8 lane motorway. The total cost of a traffic analysis system based on this technique thus increases when the zone to be monitored contains several lanes.